Using the weekly closing stock price $(S_i)$ data in the table below, find the stock price volatility per annum in decimal format $($not in $\%).$ For calculating returns, use the $S_{i-1})$ approach.

Enter your answer rounded to four decimal places. For example, if your calculation results in $0\mathrm{.}1234567,$ you only need to enter $0\mathrm{.}1234$

$\backslash$table$[[$Week$,S_i($in $$)],[1,30\mathrm{.}2],[2,32],[3,31\mathrm{.}1],[4,30\mathrm{.}1],[5,30\mathrm{.}2],[6,30\mathrm{.}3],[7,30\mathrm{.}6],[8,33],[9,32\mathrm{.}9],[10,33],[11,33\mathrm{.}5],[12,33\mathrm{.}5],[13,33\mathrm{.}7],[14,33\mathrm{.}5],[15,33\mathrm{.}5]]$